Aqueous dispersion of polymers containing polar groups and amide groups with poly(alkylene oxide)

ABSTRACT

This invention relates to aqueous dispersions of synthetic polymer particles, particularly those used as film-forming media in surface coating compositions. 
     The problem of maintaining under moist conditions the adhesion to a substrate of a film formed from a surface coating composition having such an aqueous dispersion as a film former can be substantially overcome by using a dispersion wherein the film-forming polymer comprises (a) polar groups selected from amine, ureido and thioureido groups (b) a proportion of monomer units derived from acrylamide and methacrylamide, and (c) a proportion of poly(alkylene oxide). The proportions of these components present by weight of the film-forming polymer are at least 0.3% of (a), at least 0.3% of (b), at least 0.5% of (c) and from 1.4-9.0% of (a)+(b)+(c). 
     These aqueous polymer dispersions may be used in interior or exterior surface coatings.

This invention relates to aqueous dispersions of synthetic polymers andmore particularly to aqueous dispersions of addition polymers for use insurface coatings.

Aqueous dispersions of addition polymers are well known to the art andhave been used for a number of years as film-forming media in paints andfloor polishes, as adhesives and as conditioning agents for textiles.When a coating composition comprising an aqueous dispersion of such apolymer is applied to a substrate and allowed to dry, the disperseparticles of polymer coalesce to form a continuous, tough, adherentfilm. The degree of adhesion of this film to the substrate and theextent to which this adhesion can be maintained are very much dependenton the nature of the substrate and on the conditions to which the filmwill be subjected. One combination of substrate and conditions which isespecially harsh is also very common--the direct application of thecoating to a cured paint composition, in particular a gloss alkyd paint,and subsequent exposure to moisture. This can occur, for example, in akitchen, or, in the case of an exterior substrate, when the film isexposed to moisture, especially in the first few days after application.The ability of a coating composition to withstand such severe conditionscan be assessed from a knowledge of its performance in variouslaboratory tests, for example, wet adhesion and humidity resistance(blistering) tests.

It has been found that significant improvements in moisture resistanceproperties can be made by the inclusion in some addition polymers ofcertain types of polar groups, and improved dispersions of this typehave been described in, for example, Australian Pat. Nos. 290,025 and403,662.

The fact that the addition of certain water-soluble moieties such aspoly(ethylene oxide) to aqueous dispersions can considerably modify therheology of such dispersions is known to and used by the art. An exampleof such a disclosure is Australian Pat. No. 482,559 which discloses theuse of a water-soluble poly(ethylene oxide) as a rheology modifier in athermosetting latex coating composition for use in metal decorating.However, it is also well known that the presence of such water-solublemoieties can severely impair moisture resistance properties. Forexample, in "Polymer Processes" (Vol. X of the "High Polymer" series)(Interscience, 1956) at page 107, Trommsdorff and Schildknecht teachthat in general the presence of moieties such as the condensationproducts of ethylene oxide and oleic acid impairs the water resistanceof films formed from such aqueous dispersions.

We have now made the surprising discovery that, contrary to the generalteachings outlined above, certain water-soluble moieties can be used ina particular manner to enhance further the moisture resistance ofcertain polar group-containing addition polymer dispersions.

We therefore provide, according to the present invention, an aqueousdispersion of particles of at least one film-forming addition polymer ofα,β-ethylenically unsaturated monomer at least one of which polymerscomprises a proportion of polar groups selected from amine, ureido andthioureido groups, and characterised in that

(a) the polar groups are chosen as follows;

(i) the amine groups correspond to the general formula ##STR1## whereR₁, R₂ are H, CH₃ or OH R₃, R₄ are H or C₁ -C₄ alkyl or hydroxyalkylgroups;

(ii) the ureido or thioureido groups are such that the solubility inwater of a compound consisting of such a group attached directly to amethacrylyl group is at least 1% by weight at 25° C.;

(b) at least one film-forming addition polymer comprises a proportion ofa copolymerisable amide monomer selected from acrylamide andmethacrylamide; and

(c) the film-forming polymer comprises a proportion of poly(alkyleneoxide), the poly(alkylene oxide) being soluble in water and having atleast 30 ethylene oxide units per molecule

and further characterised in that

(d) there is present in the film-forming polymer at least 0.5% by weightof the total film-forming polymer of the poly(alkylene oxide), at least0.3% of the polar groups and at least 0.3% by weight of the amidemonomer; and,

(e) the combined weights of the poly(alkylene oxide), the polar groupsand the amide monomer comprise from 1.4-9.0% by weight of the totalfilm-forming polymer.

A poly(alkylene oxide) is an entity of formula

    R--R'--CH.sub.2 --O ).sub.n H

where the nature of R' depends on the type of monomer unit from whichthe poly(alkylene oxide) is formed. For example, if the unit is anethylene oxide unit, R' will be CH₂. The identity of the terminal groupR is usually determined by the choice of starting material from whichthe poly(alkylene oxide) is prepared. It can be, for example, a hydroxylgroup or an alkoxy group. One class of materials which do not work inour invention are commercially-available surfactants wherein R is analkyl phenoxy or long chain alkyl group and these materials arespecifically excluded from our invention. For best results, we havefound that R should preferably be an alkoxy group of from one to fourcarbon atoms or more preferably a hydroxyl group. For the working of ourinvention, the poly(alkylene oxide) must comprise on average at least30, and preferably at least 50, ethylene oxide units per molecule and itmust be water-soluble. In practice, the requirement of water solubilitymeans that the poly(alkylene oxide) chain will consist predominantly ofethylene oxide units but minor proportions of other alkylene oxide unitscan be tolerated, for example propylene oxide can be incorporated inquantities of typically 10% by weight.

The film-forming addition polymer comprising the particles of theaqueous dispersions of this invention may be prepared from any of theα,β-ethylenically unsaturated monomers known to and used by the art forthe purpose of making such aqueous dispersions. Typical examples ofsuitable monomers are styrene, vinyl acetate, vinyl "versatate", vinylchloride and esters of acrylic and methacrylic acids with monohydricalcohols having 1-18 carbon atoms, for example, methyl acrylate, ethylacrylate, butyl acrylate, 2-ethyl hexyl acrylate, methyl methacrylate,ethyl methacrylate and n-butyl methacrylate. The film-forming additionpolymer may be a single addition polymer or a blend of such polymers. Wehave found that addition polymers which comprise at least 30% by weightof acrylic monomers, that is, derivatives of acrylic and methacrylicacids, perform especially well when used in our invention and these areour preferred polymers.

At least one addition polymer must comprise a proportion of polar groupswhich are chosen from amine, ureido and thioureido groups.

The amine group is selected from groups having the general formula##STR2## where R₁ and R₂ are H, CH₃ or OH, and R₃ and R₄ are H or C₁ -C₄alkyl or hydroxyalkyl groups. These groups may be derived from anethylenically unsaturated monomer comprising such a group. For example,a group of the formula

    --CH.sub.2 CH.sub.2 N(CH.sub.3).sub.2

may be provided by incorporating into the polymer a suitable proportionof dimethylaminoethyl methacrylate. ##STR3##

Alternatively, the amine group may be provided by the reaction of areactive group on the polymer with a compound which bears both acomplementary reactive group and an amine group, or a group which iscapable of generating the amine group. A very convenient way ofproviding a suitable amine group is by reacting a carboxyl group on thepolymer (provided by, for example, methacrylic acid) with a compoundbearing an aziridine group. In this case, the amine group is actuallygenerated during the reaction. A further example of a suitable reactionwould be that of an oxirane group on the polymer (provided by, forexample, glycidyl methacrylate) with ammonia.

Ureido and thioureido groups are chosen such that a compound whichconsists of one of these groups and a methacrylyl group has a solubilityin water at 25° C. of at least 1% by weight. Thus, a ureido group havingthe formula ##STR4## is encompassed by our invention, as a compoundconsisting of both this group and a methacrylyl group,N-methacryloxyacetamidoethyl-N,N'-ethylene urea ##STR5## iswater-soluble to the required degree. On the other hand, a group of theformula ##STR6## is not encompassed by our invention as the compoundconsisting of this group and a methacrylyl group,N-t-butyl-N-methacryloxyethyl-N'-butyl urea, is not water soluble to therequired degree.

Ureido and thioureido groups may be provided by the incorporation of asuitable ureido or thioureido group-bearing monomer such as thatmentioned above into the polymer. Alternatively, they may be providedby, for example, the reaction of a compound comprising both a suitableureido or thioureido group and a reactive group with a complementaryreactive group on the polymer.

At least one film-forming addition polymer must comprise a proportion ofa copolymerisable amide monomer which is selected from acrylamide andmethacrylamide. We believe, without placing any restrictions on thescope of our invention, that the poly(alkylene oxide) associates in someway with the amide monomer and that this association in combination withthe polar groups gives the resultant film-forming dispersionsadvantageous properties which are not exhibited by dispersions lackingone or more of these three components. It is noteworthy that thereplacement of acrylamide or methacrylamide by another polar monomersuch as acrylonitrile or methacrylic acid results in a dispersion whichdoes not have the advantageous properties.

The quantities of poly(alkylene oxide), polar groups and amide monomerpresent must comply with certain limits with respect to the total weightof film-forming disperse polymer. For example, the poly(alkylene oxide)must be present to the extent of at least 0.5% by weight of thefilm-forming polymer, the polar groups to the extent of at least 0.3% byweight and the amide monomer to the extent of at least 0.3% by weight.Further, the combined weights of the poly(alkylene oxide), the polargroups and the amide monomer must comprise between 1.4% and 9.0% byweight of the film-forming polymer.

We have observed that there is no sharp change at these limits--there isa gradual change in properties as the combined weight percentage isaltered--but we have selected these limits because they permit us toformulate aqueous polymer dispersions having both the excellent moistureresistance properties of our invention and acceptable film properties.Our preferred range of combined weight percentages is 1.7%-6%; in thisrange the optimum properties are achieved.

The poly(alkylene oxide) may be blended with the dispersion of polymerparticles, the polymer of which particles comprises the polar groups andamide monomer, but we have found that the best results are achieved ifthe dispersion of particles of polymer comprising the amide monomer isprepared in the presence of the poly(alkylene oxide). It is permissibleto have both the polar groups and the amide monomer incorporated into asingle addition polymer or into separate addition polymers which arethen blended. Such a single addition polymer or such a blend may be usedin the form of an aqueous dispersion of particles as the solefilm-forming component of a coating composition, or it may be blendedwith a conventional aqueous addition polymer dispersion which does notcontain such species. For example, an aqueous dispersion of an additionfilm-forming polymer comprising 2.0% by weight of poly(alkylene oxide),1.4% of polar groups and 0.6% of the amide monomer will display all theadvantages of the present invention not only when used as the solefilm-forming component of a coating composition, but also when it isblended with an equal proportion of an otherwise identical dispersionwhich lacks all three components--in this latter case, the overallindividual concentrations of the poly(alkylene oxide) the polar groupand the amide monomer are 1.0% and 0.7% and 0.3% respectively and theirtotal is 2.0%, all of which fall within the limits as hereinabovedefined.

The aqueous dispersions of polymer particles of this invention may beprepared using processes and techniques well known to the art. Additivessuch as thickening agents, surfactants and stabilisers which arecommonly used in such processes may be used in art-recognised quantitiesin the preparation of aqueous dispersions according to the invention.These dispersions may be incorporated directly into coating compositionsby conventional means, and normal paint ingredients such as pigments,extenders and thickeners may be incorporated in art-recognisedquantities in the conventional manner.

The use of our invention enables persons skilled in the art to prepareaqueous dispersions exhibiting commercially acceptable moistureresistance properties using levels of polar groups which are too lowaccording to the normal practices of the art. This may represent asubstantial cost saving as the need for increased use of expensive polargroup-containing compounds is removed. Many of these polar groups,notably those derived from aziridine groups, have a marked tendency tocause "yellowing" of compositions in which they are included. Thereduction of the number of polar groups required for good wet adhesionwill also lead to a reduction in yellowing tendencies. Alternatively,the invention may be used to enhance further the moisture resistanceproperties of a polar group-containing polymer dispersion alreadyexhibiting good moisture resistance properties. It is a feature of ourinvention that paint compositions incorporating aqueous polymerdispersions according to our invention exhibit very good moistureresistance properties, often at least equal and even superior to thoseof the best of the currently available commercial compositions.

The invention is further illustrated by the following examples in whichall parts are expressed by weight.

EXAMPLE 1

Preparation of an aqueous dispersion of film-forming addition polymerwhich comprises 0.68% by weight of amine groups, 0.5% by weight of amidemonomer and 1.0% by weight of poly(alkylene oxide).

(a) Preparation of dispersion

The following materials and quantities were used;

    ______________________________________                                        A   Distilled water           208.08  parts                                       Non-ionic low foaming surfactant                                              (poly(ethylene oxide-propylene                                                oxide) adduct)*           3.31                                                Hydroxy ethyl cellulose (low                                                  viscosity grade)          2.04                                                Poly(ethylene glycol) (molecular                                              weight 4,000)             4.84                                            B   Distilled water           191.06                                              Sodium dodecyl benzene sulphonate                                             surfactant*               1.87                                                Sodium dicyclohexyl sulphosucc-                                               inate surfactant ***      0.93                                                Non-ionic octyl phenol ethoxylate                                             surfactant.sup.+          3.31                                                Methyl methacrylate       262.32                                              Butyl acrylate            217.71                                              t-dodecyl mercaptan       0.97                                             *for example, "Teric38 0 PE64 (trade mark)                                    **for example, "Spionate" DS10 (trade mark)                                   *** for example, "Aerosol" A196 (trade mark)                                  +for example, "Triton" X405 (trade mark)                                 

        0.880 ammonia solution    2.43    parts                                       Acrylamide                2.43                                            C   Dimethyl aminoethyl methacrylate                                                                        7.30                                            D   Distilled water           3.11                                                Ammonium persulphate      0.97                                            E   Distilled water           3.11                                                Ammonium persulphate      0.68                                                4% of B                   27.23                                           F   Distilled water           0.49                                                Ammonium persulphate      0.08                                            G   Distilled water           64.42                                               Bactericide               0.08                                            ______________________________________                                    

The procedure was as follows:

The materials A were charged to a reaction vessel equipped with aheating mantle, stirrer and means for passing nitrogen. The vessel washeated with continuous agitation to 78° C. (at which temperature it washeld throughout the reaction) and the passing of nitrogen was started.The materials D were added followed 15 minutes later by the materials E.After a further 15 minutes, 80% of the remaining materials B wascontinuously fed into the reaction mixture over a period of 21/2 hours.The remaining 20% of the materials B was then blended with the materialsC and this blend continuously added over a period of 35 minutes. Thematerials F were added 30 minutes after the completion of the additionof the blend. The reaction mixture was allowed to agitate for a further30 minutes and then cooled to about 32° C., at which point the materialsG were added and the mixture allowed to cool to room temperature.

The resultant composition was a white aqueous dispersion of weightsolids content 50.7%.

EXAMPLE 2

Comparative testing of the aqueous dispersion of Example 1.

Two types of testing were used, a wet adhesion test and a humidity test.

Wet Adhesion Test

The test method used was as follows:

(i) a panel of hardboard was primed and sprayed with an alkyd enamel;

(ii) the panel was allowed to dry for three days and then bakedovernight at 65° C.

(iii) a 175 μm film of a mixture of aqueous dispersion and tri-n-butylphosphate (added at the rate of 2.8 g per 100 g dispersion) was drawndown on the panel and air dried for 24 hours.

(iv) the film was scribed with a single longitudinal scribe and thencross-scribed on this scribe;

(v) the panel was immersed in water for an hour and withdrawn, excesswater was wiped off, adhesive tape was applied to the cross-scribes andthen immediately pulled off. The result was visually rated on a scale offrom 1 to 5 where 5 represents no removal of film and 1 representsremoval of the film over the entire area of contact of the tape.

Humidity Test

Panels prepared according to steps (i)-(iii) of the wet adhesion testwere suspended vertically in a humidity cabinet at 38° C. and 100%humidity for 2 weeks. The films were assessed for whitening (believed tobe caused by the formation of water droplets within the film) blisteringand gloss--an ideal panel should exhibit no whitening, no blistering andno loss of gloss.

The aqueous addition polymer dispersion prepared in Example 1 wassubjected to these tests along with the following dispersions;

(a) an otherwise identical aqueous dispersion lacking poly(alkyleneoxide) chains.

(b) an otherwise identical aqueous dispersion lacking polar groups;

(c) an otherwise identical aqueous dispersion lacking amide monomer;

(d) an otherwise identical aqueous dispersion lacking both amide monomerand poly(alkylene oxide) chains;

(e) a commercially available aqueous acrylic dispersion (the dispersionused was AC508 (ex Rohm & Haas Co.) a proprietary acrylic latex of 46.5%solids)

The results of the testing are given in the following table--the glossof all films prior to humidity testing was rated as "good"

    ______________________________________                                                Wet Adhesion                                                                            Humidity Performance                                                testing   Whitening Blistering                                                                             Gloss                                    ______________________________________                                        Dispersion                                                                    according                                                                     to the invention                                                                        5           None      None   good                                   Dispersion (a)                                                                          2           V.white   50% of v. poor                                                                surface                                       Dispersion (b)                                                                          1*          V.white   50% of good                                                                   surface                                       Dispersion (c)                                                                          2           V.white   50% of v. poor                                                                surfaceS                                      Dispersion (d)                                                                          2           V.white   80% of v. poor                                                                surface                                       Dispersion (e)                                                                          4           V. white  None   fair                                   ______________________________________                                         *In this case, the entire latex film peeled off, not only that part           contacted by the tape.                                                   

It can readily be seen that the dispersion comprising a combination ofpolar groups, amide monomer and poly(alkylene oxide) chains gave resultswhich were better than those obtained from a good commercial aqueousdispersion and superior to those of dispersions lacking one or more ofthese essential elements.

EXAMPLE 3

The effect of blending two aqueous dispersions of polymer particles, thepolymer of one dispersion comprising 1.37% by weight of polar groups,the polymer of the other comprising 2% by weight poly(alkylene oxide)chains and 1% by weight of amide monomer.

Two aqueous dispersions were prepared according to the method and usingthe materials of Example 1 except that one dispersion comprised 1.37% byweight of polar groups and no poly(ethylene oxide) chains or amidemonomer, and the other dispersion 2% by weight poly(ethylene oxide)chains, 1% by weight of amide monomer and no polar groups. Thedispersions were blended in equal weight proportions and tested asdescribed in Example 2. The blend exhibited the same excellentproperties as the aqueous dispersion prepared in Example 1.

EXAMPLE 4

Demonstration of the necessity for adhering to the stated parameters.

A number of aqueous addition polymer dispersions were prepared accordingto the method of Example 1 in which the proportions of polar groups,amide monomer and poly(alkylene oxide) chains (expressed as a percentageby weight of the polymer) were varied. The resultant aqueous dispersionswere subjected to the adhesion test described in Example 2 and theresults are shown in the following table.

    ______________________________________                                        Dis-                   poly(alky-                                                                            Total %   Wet                                  per-                   lene oxide                                                                            amide monomer                                                                           Adhe-                                sion % polar  % Amide  chains  polar groups                                                                            sion                                 No.  groups   monomer  %       & chains  Rating                               ______________________________________                                        1    0.23     0.5      1.0     1.73      1                                    2    0.46     0.1      1.0     1.56      1                                    3    0.46     0.3      0.3     1.06      1                                    4    0.46     0.3      0.5     1.26      2                                    5    0.46     0.5      0.5     1.46      3                                    6    0.57     0.25     1.0     1.82      4                                    7    0.46     0.3      1.0     1.76      5                                    8    0.68     0.5      1.0     2.18      5                                    9    0.68     1.0      1.0     2.68      5                                    10   0.91     1.5      3.0     5.41      5                                    11   2.28     1.0      5.0     8.78      4                                    ______________________________________                                    

It can readily be seen that a dispersion which has a proportion of polargroups, amide monomer or poly(alkylene oxide) chains lower than thespecified limits of 0.3%, 0.3% and 0.5% respectively (dispersions nos.1, 2 and 3 respectively), or which has a total proportion of polargroups, amide monomer and poly(alkylene oxide) chains lower than thespecified limit of 1.4% (dispersion no. 4), will give a relatively poorwet adhesion result. A borderline case such as Dispersion 5 will give animproved result and Dispersions 7-10, which lie within the preferredtotal proportion range of 1.7%-6%, all show excellent wet adhesionresults. The wet adhesion properties of Dispersion 11, which has a totalproportion of polar groups and poly(alkylene oxide) chains lying withinthe scope of the invention but outside the preferred range, show somefalling-off relative to those of the dispersions lying within thepreferred range, but still remain very good.

EXAMPLE 5

This example illustrates the use of different polar groups.

This example illustrates the use of different polar groups.

A number of aqueous addition polymer dispersions were prepared accordingto Example 1 substituting appropriate quantities of the followingmonomers for the dimethylaminoethyl methacrylate such that thequantities of polar groups in all cases were equivalent to that ofExample 1.

(a) t-butylaminoethyl methacrylate;

(b) N-methacryloxyacetamidoethyl-N,N'-ethylene urea;

(c) N-t-butyl-N-methacryloxyethyl-N'-butyl urea;

where

monomers (a) and (b) lie within the scope of the invention; and

monomer (c) is a ureido group-containing monomer which is not watersoluble to the required extent of 1% at 25° C.

The dispersions prepared therefrom were subjected to the wet adhesiontest as described in Example 2 and the results were as follows:

    ______________________________________                                        Monomer         Wet Adhesion Rating                                           ______________________________________                                        (a)             5                                                             (b)             5                                                             (c)             2                                                             ______________________________________                                    

It is readily apparent that only the polar monomers according to theinvention give desirable results.

EXAMPLE 6

Preparation of an aqueous polymer dispersion wherein the polymercomprises 1% by weight of poly(ethylene oxide) chains (molecular weight4,000), 0.5% by weight of amide monomer, and 0.68% by weight of polargroups provided by the reaction of carboxyl groups on the polymer with acompound bearing an aziridine group.

(a) Preparation of dispersion

The materials and quantities and procedures used in this preparationwere identical to those of Example 1 except that an identical weight ofmethacrylic acid was substituted for the dimethylaminoethylmethacrylate.

The resulting aqueous dispersion had a solids content of 50.5%.

(b) Provision of polar groups

The materials used were as follows;

Aqueous dispersion (as prepared above): 700 parts

1,2-propyleneimine: 6.9 parts

The 1,2-propyleneimine was added gradually with stirring to the aqueousdispersion at room temperature. Stirring was continued for an hour afterwhich the temperature was raised to 80° C., held there for a further11/2 hours, and then cooled slowly.

The resulting aqueous dispersion had a solids content of 51.2% and nofree imine.

(c) Testing

Imine groups are known to be excellent as adhesion promoters, but theyare also known to confer "yellowing" characteristics on dispersions inwhich they are incorporated. It was believed that the use of polargroups derived from imines in conjunction with poly(ethylene oxide)chains would permit the use of a lower concentration of imine-derivedpolar groups than was normally acceptable for good adhesion and stillpermit the production of dispersions with both acceptable humidityperformance and lowered yellowing tendencies. To this end, a "blank"aqueous dispersion was prepared as described in section (a) above, butomitting the poly(ethylene oxide) chains, amide monomer and methacrylicacid, and this was used to dilute the iminated dispersion at a rate of50 parts of "blank" to 50 parts of dispersion according to theinvention.

A "control" dispersion was prepared according to sections (a) and (b)above, but the poly(ethylene oxide) chains and amide monomer wereomitted. This was tested in two forms, undiluted and diluted 50/50 with"blank".

The testing methods were those used in Example 2 except that in thehumidity test, the films were assessed for yellowing rather thanwhitening.

The results are summarised in the following table;

    ______________________________________                                                   Wet    Humidity Performance                                                   adhesion          Blist-                                                      rating Yellowing  ering   Gloss                                    ______________________________________                                        Dispersion according                                                          to the invention                                                                           5        Considerable                                                                             none  good                                   "Control" dispersion                                                                       4        Considerable                                                                             none  fair                                   Dispersion according                                                                       3        Slight     5% of good                                   to the invention                 surface                                      diluted 50/50 with                                                            "blank" dispersion                                                            "Control" dispersion                                                                       2        Slight     5% of poor                                   diluted 50/50 with               surface                                      "blank" dispersion                                                            ______________________________________                                    

The table shows that although the dispersion according to the inventionhas excellent blistering resistance, gloss retention and wet adhesion,it is very prone to yellowing. The diluted dispersion according to theinvention does not show the same excellent properties but the propertiesremain commercially acceptable and the diluted sample does not have theundesirable yellowing of the undiluted dispersion. Both of thesedispersions are superior to the respective "control" dispersions whichdo not have poly(ethylene oxide) chains.

EXAMPLE 7

Demonstration of the effect of changing the nature of the poly(alkyleneoxide) chains.

Several aqueous dispersions were prepared and tested using thematerials, quantities and method of Examples 1 and 2 except that in eachcase the poly(ethylene oxide) chains were substituted by an amount ofone of the following materials such that the dispersions contained 1% byweight of poly(alkylene oxide) chains;

    ______________________________________                                                   Wet     Humidity Performance                                                  Adhesion          Blist-                                                      Rating  Whitening ering   Gloss                                    ______________________________________                                        Poly(ethylene oxide)                                                                       2         some      20% of                                                                              fair                                   (Molecular wt. 600)              surface                                      Methoxypoly(ethylene                                                                       2         some      20% of                                                                              fair                                   oxide)                                                                        (Molecular wt 750)                                                            Poly(ethylene oxide)                                                                       5         none      none  good                                   (Molecular wt 4,000)                                                          Poly(ethylene oxide)                                                                       5         none      none  good                                   (Molecular wt 6,000)                                                          Poly(ethylene oxide/                                                                       5         none      none  good                                   propylene oxide)                                                              (Molecular wt 4,100)                                                          Non-ionic surfactant*                                                                      1         severe    100% of                                                                             very                                   comprising about                 surface                                                                             poor                                   40 ethylene units                                                             (poly(ethylene oxide)                                                         molecular wt about 1,760)                                                     ______________________________________                                         *A commercial material "Triton X405" was used ("Triton" is a trade mark) 

It can readily be seen from this example that those poly(ethylene oxide)chains having a molecular weight below about 1000 (about 30 ethyleneoxide units) give poor adhesion. In addition, the commercial surfactant,which comprises a poly(ethylene oxide) chain of the correct size is theworst performer of all. Only those poly(alkylene oxide) chains whichcomply with the invention give satisfactory performance.

EXAMPLE 8

Preparation of a non-acrylic aqueous dispersion according to theinvention.

An aqueous dispersion of a copolymer of vinyl acetate and butyl acrylatein the ratio 80:20 was prepared in the presence of hydroxyethylcellulose protective colloid and anionic surfactant using methods knownto the art. In addition, the polymer comprised 1.37% polar groups(derived from dimethylaminoethyl methacrylate), 1% amide monomer(acrylamide) and 2% poly(ethylene oxide) chains of molecular weight4000. The dispersion had a weight solids content of 59.0%.

This dispersion was subjected to the wet adhesion test of Example 2together with two similar dispersions, one lacking amide monomer andpoly(ethylene oxide) chains and the other lacking polar groups, amidemonomer and poly(ethylene oxide) chains, the latter of course being aconventional poly(vinylacetate/butyl acrylate) dispersion of the typewidely used in the art.

    ______________________________________                                                           Wet Adhesion Rating                                        ______________________________________                                        Dispersion according to invention                                                                  5                                                        Dispersion lacking acrylamide and                                             poly(ethylene oxide) chains                                                                        2                                                        Dispersion lacking acrylamide, polar                                          groups and poly(ethylene oxide) chains                                                             2                                                        ______________________________________                                    

The aqueous dispersion according to the invention gave results superiorto those given by either of the two comparative dispersions.

EXAMPLE 9

Preparation and comparative testing of a coating composition comprisingan aqueous dispersion according to the invention.

The coating composition prepared was a gloss white formulation forexterior use.

A base was prepared by blending the following materials until pigmentdispersion was complete.

    ______________________________________                                        Water                   11.54 parts                                           Sodium hexametaphosphate                                                                               0.38                                                 Titanium dioxide pigment                                                                              23.00                                                 Hydroxyethyl cellulose   0.14                                                 Tributyl phosphate       1.58                                                 ______________________________________                                    

The following materials were then blended to give a coating composition.

    ______________________________________                                        Base (as prepared above)                                                                              41.90 parts                                           Aqueous dispersion (from                                                      example 1)              52.33 "                                               Water                    5.77 "                                                                       100.00                                                ______________________________________                                    

The base was also used to prepare in an identical manner, coatingcompositions from the aqueous dispersions (d) and (e) of Example 2, thewater quantity being adjusted to give 100 parts.

The coating compositions were subjected to the wet adhesion test ofExample 2. The compositions based on aqueous dispersions (d) and (e) ofExample 2 failed over most of the area contacted by the tape but thecomposition based on the aqueous dispersion according to the inventionshowed no failure.

We claim:
 1. An aqueous dispersion of particles of at least onefilm-forming addition polymer of α,β-ethylenically unsaturated monomerat least one of which polymers comprises a proportion of polar groupsselected from the group consisting of amine, ureido and thioureidogroups, and characterised in that(a) the polar groups are chosen asfollows;(i) the amine groups correspond to the general formula ##STR7##where R₁, R₂ are H, CH₃ or OHR₃, R₄ are H or C₁ -C₄ alkyl orhydroxyalkyl groups; (ii) the ureido or thioureido groups are such thatthe solubility in water of a compound consisting of such a groupattached directly to a methacrylyl group is at least 1% by weight at 25°C.; (b) at least one film-forming addition polymer comprises aproportion of copolymerisable amide monomer units selected from thegroup consisting of acrylamide and methacrylamide; and (c) the aqueousdispersion comprises a proportion of poly(alkylene oxide), thepoly(alkylene oxide) being soluble in water and having at least 30ethylene oxide units per moleculeand further characterised in that (d)there is present in the dispersion at least 0.5% by weight of the totalfilm-forming polymer of the poly(alkylene oxide) at least 0.3% of thepolar groups and at least 0.3% by weight of the amide monomer units;and, (e) the combined weights of the poly(alkylene oxide), the polargroups and the amide monomer units comprise from 1.4-9.0% by weight ofthe total weight of the film-forming polymer and poly(alkylene oxide).2. An aqueous dispersion of addition polymer particles according toclaim 1, characterised in that the polar groups in the polymer areprovided by the incorporation in the polymer of α,β-ethylenicallyunsaturated monomer bearing such groups.
 3. An aqueous dispersion ofaddition polymer particles according to claim 1, characterised in thatthe polar groups in the polymer are provided by the reaction of reactivegroups on the polymer with a compound bearing a complementary reactivegroup and in addition which bears or is capable of generating such apolar group.
 4. An aqueous dispersion of addition polymer particlesaccording to claim 2, characterised in that the monomer is chosen fromthe group consisting of dimethylaminoethyl methacrylate, t-aminoethylbutyl methacrylate and N-methacryloxyacetamidoethyl-N,N'-ethyl urea. 5.An aqueous dispersion of addition polymer particles according to claim3, characterised in that the reactive groups on the polymer are carboxylgroups and the compound bears an aziridine group.
 6. An aqueousdispersion of addition polymer particles according to claim 1,characterised in that the addition polymer comprises at least 30% byweight of acrylic and methacrylic monomer units.
 7. An aqueousdispersion of addition polymer particles according to claim 1,characterised in that the combined weight of polar groups, amide monomerunits and poly(alkylene oxide) chains comprises from 1.7%-6% of thetotal weight of the film-forming addition polymer and poly(alkyleneoxide).